Spacer damper

ABSTRACT

A cable damper for damping vibrations in two parallel electrical cables has a main body and two arms mounted thereon. The arms carry cable clamping means for holding the two cables and are mounted on the body by pivotal mountings which allow for pivotal movement of the arms only about predetermined axes parallel to the cables held by said arms. The pivotal mountings for the arms include resilient energy absorbing means biasing the arms into neutral positions in which positions the arms are inclined to the common plane of said cables. The inclinations are such that the range of angular movement of an arm about said neutral position such as can be caused by vibrations of a cable attached thereto lies between planes through the pivotal aXis of said arm respectively parallel to and perpendicular to said common plane.

United States Patent Herbert James Houston Oakville, Ontario;

Robert Gordon Baird, Burlington, Ontario; Kenneth Dale Bolt, Burlington,Ontario; Adolf Gretzinger, Ancaster, Ontario, all of [72] InventorsCanada [21] Appl. No. 830,002 [22] Filed June 3, 1969 [45] PatentedSept. 28, 1971 N. Slater Company, Division of Slater Steel IndustriesLimited [32] Priority Apr. 9, 1969 [3 3 Canada [73] Assignee [54] SPACERDAMPER 11 Claims, 7 Drawing Figs.

[5 6] References Cited UNITED STATES PATENTS 10/1969 Crosby et al3,475,544 10/1969 Reed 174/42 OTHER REFERENCES Wigotsky, Silicone-RubberWashers Soothe Vibrating Transmission Lines, Design News, Aug. 18, 1965,pages 1 14 and 115. Copy in 174- 42.

Primary ExaminerLaramie E. Askin Attorney-LeBlanc & Shur ABSTRACT: Acable damper for damping vibrations in two parallel electrical cableshas a main body and two arms mounted thereon. The arms carry cableclamping means for holding the two cables and are mounted on the body bypivotal mountings which allow for pivotal movement of the arms onlyabout predetermined axes parallel to the cables held by said arms. Thepivotal mountings for the arms include resilient energy absorbing meansbiasing the arms into neutral positions in which positions the arms areinclined to the common plane of said cables. The inclinations are suchthat the range of angular movement of an arm about said neutral positionsuch as can be caused by vibrations of a cable attached thereto liesbetween planes through the pivotal aXis of said arm respectivelyparallel to and perpendicular to said com mon plane.

PATENTEU SEP28 Ian saw 2 0F 6 m ls PATENTED 8928 I9" sum 5 OF 6 SPACERDAMPER The present invention relates to cable dampers for overheadelectrical transmission lines.

When the cables of a transmission line span long distances betweenadjacent pylons, wind effects on the cables may cause these to vibrate.Vibrations in such cables may take several forms, the type of greatestimportance being referred to as aeolian vibration.

ln overhead systems having a single wire or cable, aeolian vibrationoccurs in relatively light winds, usually from 1 to 15 miles per hourandresults from eddies which form on the lee side of the cable. When thefrequency of the eddies coincides with one of the many naturalfrequencies of the cable, the forces arising from the eddies causes thecable to vibrate generally in the vertical plane. This type of vibrationis often present for about 50 percent of the time and if permitted tooccur without adequate control will result in mechanical failure of thewire or cable, sometimes within a very short period of time.

Transmission lines of today often include several subconductors for eachpole or phase, the subconductors being grouped in "bundles." in thistype of transmission line, not only does the type of aeolian vibrationdescribed above occur, but in addition wind flow over the windwardconductor may cause an eddy-vortex system between the adjacentsubconductors in the same horizontal plane such as will impart a drivingforce to the leewards conductor or conductors causing these to vibrateor oscillate in the horizontal plane. This vibration once initiated mayconvert to a vibration in a plane other than the horizontal, for exampleat 45 to the vertical. This horizontal vibration may be initiated whenthe ratio of the conductor or cable diameter to the spacing betweenconduc tors or cables is less than about 30 to l or may become extremelypronounced when the ratio is in the neighborhood of 10 to l. Themechanism of the horizontal vibration is very similar to that of theaeolian vibration described above for a single conductor in that thedriving force imparted by the eddy-vortex combination will coincide withone of the many natural frequencies of the conductor or cable, causingsustained vibration. The vibrations so caused may be such that theresulting standing waves are in phase for adjacent cables, or the wavesmay be 180 out of phase. External forces such as ice falling from onesubconductor and not the other may cause cyclic movement of onesubconductor with respect to the otherin the direction of thelongitudinal axes of the cable. This motion is generally known in theindustry as differential longitudinal motion. The present invention isso constructed as to accommodate this motion.

Where each pole or phase consists of a bundle of several subconductorsor cables, it is known to provide spacers situated at intervals alongeach span, which hold the individual conductors apart and prevent damagewhich would otherwise occur by cables of a bundle clashing against eachother. However, such spacers of themselves will not necessarily preventthe above-described oscillatory motion, which may still occur either inthe subspans between the spacers, or in the complete span withconsequent movement of the spacers.

To prevent subspan clashing of the cables the spacers must be placed atintervals along the span usually between 200 and 300 feet apart, withshorter spans adjacent the suspension points. The provision of suchspacers at these intervals is essential to prevent the conductors fromclashing, quite apart from any damping requirement, but it is convenientto use these spacers also as dampers rather than to use larger and lessmanageable dampers situated only at the suspension points. Spacers whichact as dampers for this purpose are known, which are designed to bespaced along the span between the suspension points, and such spacerdampers differ from devices which are concentrated at the suspensionpoints at the ends of a span.

Known spacer dampers include devices which dissipate vibrational energyby twisting the cables so causing the cable strands to rub against eachother and frictionally dissipate the energy of vibration. There are alsoknown spacer dampers for attachment to a group of parallel cables of thesame pole or phase, such dampers generally having a main body attachedto the cables by short arms having cable clamps, the arms beingconnected to the main body by energy absorbing devices which allowlimited angular movement between the arms and the body while absorbingthe energy of such movements, and so damping the vibrations. The presentinvention relates to cable dampers of this latter type.

Known spacer dampers of this type dissipate energy from longitudinalvibrations in the cables, and in some cases vertical transversevibrations in the cables are also damped. The present invention,however, provides a spacer damper which is effective to damp outtransverse vibrations in cables attached thereto both in the horizontaland vertical planes, and this form of damping has been found to be muchmore effective than that of known dampers.

According to the present invention, a cable damper for dampingvibrations in two parallel electrical cables, comprises a main body, andtwo arms mounted thereon, said arms carrying cable clamping means forholding the two cables, the arms being mounted on the body by pivotalmountings which allow for pivotal movement of the arms only aboutpredetermined axes parallel to the cables held by said arms, the pivotalmountings for the arms including resilient energy absorbing meansbiasing the arms into neutral positions in which positions the arms areinclined to the common plane of said cables, the inclinations being suchthat the range of angular movement of an arm about said neutral positionsuch as can be caused by vibrations of a cable attached thereto liesbetween planes through the pivotal axis of said arm respectivelyparallel to and perpendicular to said common plane.

The neutral positions are those taken up by the arms when the cabledamper is not being stressed by any vibration in the cables.

The inclination of the cable holding arms to the common plane of thecables is to be understood as meaning the angle between the said commonplane and the longitudinal axis of each arm passing through its pivotand through the center of a cable held in the clamping means. in thepreferred embodiment of this invention, this angle of inclination is 45for each arm when the arms are in their neutral positions. In this case,the pivotal movement of the arms having cables attached thereto abouttheir neutral positions will be accompanied by transverse movement ofthe cables relative to the main body which movement will havesubstantially equal components both parallel to the said common plane ofthe cables and perpendicular thereto.

However, beneficial results in accordance with this invention can alsobe achieved where the movement of cables attached to the arms, relativeto the main body, has components of the same order of magnitude bothparallel to the said common plane of the cables and perpendicularthereto. This may be achieved with inclinations of the arms (in theirneutral positions) to the said common plane lying between 25 and 65. Themovement of the arms from their neutral positions will preferably belimited to about 18, and will normally be less so that with theinclinations of the arms in their neutral positions lying between theselimits, the range of movement of an arm will always be within the limitsset by planes through the pivotal axis of said arm respectively parallelto and perpen dicular to the said common plane.

It is envisaged that the main body of the cable damper will generally bedisposed horizontally, and with the anns set at 45 to the said commonplane the cables attached thereto will have substantially equalcomponents of movement, relative to the main body, both in thehorizontal and vertical planes. The actual movement of the cables willdepend, however, on the motion of the main body, and this will depend onthe phasing of the vibrations in the cables. The spacer damper may alternatively be mounted with its main body vertical, between a horizontallydisposed pair of cables.

The main body of the cable damper may be straight, in which case theanus (assuming these are of equal length) will preferably lie at 45 tothe main body. However, the main body may be a curved member in whichcase the arms may extend in the same directions as the ends of the body.

The cable damper has been defined by reference to its connection to twocables, but dampers within the scope of the invention may be used withmore than two cables. In this case the main body will be in the form ofa frame having arms for holding each cable in addition to the two armsreferred to, so that all the cables held by such arms can vibrate bothparallel to the said common plane and perpendicular thereto.

A further feature of the present invention is the use of a main body ofsufiicient inertial mass, so that vibrations in the cables tend to causemovement of the arms on the body rather than undue movement of the bodyitself, whereby the vibrations are effectively damped.

The invention will now be described by way of example with reference tothe accompanying drawings, in which:

FIG. 1 is a side elevation of a cable damper according to the invention,

FIG. 2 is a partial cross section on line lll1 of FIG. 1,

FIG. 3 is a view on line 111-111 of FIG. 1,

FIG. 4 is a side elevation of a second embodiment of cable damperaccording to the invention,

FIG. 5 is a side elevation of a third embodiment of cable damperaccording to the invention,

FIG. 6 is a side elevation of a fourth embodiment of cable damperaccording to the invention, and

FIG. 6a is a section take along the line VlaVla of FIG. 6.

Referring now to FIGS. 1-3, a spacer damper is shown for holding a pairof adjacent cables 1 and 2, both of the same electrical potential. lnpractice, several similar spacer dampers will be spaced along the samepair of cables in each span connecting neighboring pylons, and furtherdampers will be used for other pairs of cables of different pole orphase.

The spacer damper comprises a main body 10 of, for example, forgedsteel, having at each end a flattened tongue 11. Each tongue 11 is partcircular in shape, and has a central bore surrounded on both sides ofthe tongue by an annular area of radial corrugations indicated at 12.

The main body 10 is sufficiently heavy to have an inertial masseffective for damping purposes.

At each end of the body 10 a cable clamp arm is mounted in a manner tobe described, so as to be pivotal about an axis indicated at 13 passingthrough the central bore of each tongue 11 and extending parallel to thecables 1 and 2. As shown, the arms 15 are inclined to the common planeof the cables 1 and 2, and the drawing shows the neutral positions ofthe arms in which the axis of each arm joining the center of the clampedcable to the pivotal axis 13 of the arm lies at approximately 45 to thiscommon plane, which in this case is parallel to the main body 10.

The main part of arm 15 is a casting 16, for example, of aluminum whichincludes a cylindrically grooved portion 17 forming one-half of a cableclamp, and which has an integral extension in the form of a centrallybored sideplate 18 which, on assembly, overlaps with the tongue 11 ofthe main body. On the opposite side of tongue 11 to the sideplate 18 isarranged a separate sideplate 20 similar to plate 18 and also centrallybored, and which fits into a suitably shaped recess in the side of thecasting 16. The innner faces of the sideplate extension 18 and sideplate20 both have annular areas of radial corrugations surrounding thecentral bores, matching the facing corrugations of the tongue 11. Thecasting l6 and sideplate 20 engage with each other, as by means of thesideplate extension 21, to define a predetermined space between theopposed corrugated faces.

Between the adjacent corrugated faces of the sideplates 18 and 20 andtongue 11 are held two thick elastomer washers 22 of nonconductingsilicone rubber or other suitable material. These washers 22 have radialcorrugations in their side faces which engage with the corrugations ofthe adjacent faces of the sideplates l8 and 20 and tongue 11. Thesecorrugated faces are all held in tight engagement by a bolt 24 passingthrough the bores of the sideplates 18 and 20 and through the centers ofwashers 22 and the bore of the tongue 11, the bolt having at its outerend a nut 25 holding a lock washer in engagement with the outside of theplate 20. The nut 25 holds the casting 16 and the sideplate 20 togetherin such a manner that the washers 22 are compressed into thepredetermined spaces between the tongue 11 and the inner faces ofsideplates 18 and 20. The washers are of such thickness, in relation tothis space, as to be compressed by between 18 percent and 25 percent oftheir original thickness, the material of the washers having suitableresilient and damping properties within this range. With thiscompression the engagement of the corrugated faces of the washers andthe metal parts is such as definitely to preclude slipping between thesesurfaces due to pivotal movement of the arms which occurs in practice.Thus any force tending to move the clamp arm 15 about the pivot formedby the bolt 24 is resisted by shear forces in the washers 22, which biasthe arms into their neutral position as shown and also absorb energyduring this movement.

Pivoting of the arms 15 on the body 10 is limited to an angle of about18 on each side of the neutral position by engagement between the mainbody of casting 16 and shoulders 23 on the tongue 11 at each end of thebody 10. These means prevent excess movement of the arms which mightotherwise cause damage to the rubber washers when short circuits imposeextremely high forces between the adjacent cables.

The central bore of tongue 11 is slightly larger than the insidediameter of the washers 22. Before assembly of the parts just described,a small sleeve 27 of semiconducting material is inserted into the boreof the tongue 11, in which it fits tightly, and when the washers 22 areassembled on either side of the tongue 11 these'hold the sleeve 27 inplace. The internal diameter of sleeve 27 makes close contact with theshank of bolt 24 and when the parts are assembled as shown thesemiconducting sleeve 27 forms an electrically conducting path betweenthe electrically conducting body 10 and the arm 15, so that a limitedcurrent can flow between the main body and each arm. This conductingpath reduces the potential differences between the adjacent parts, whichtend to occur by reason of the electric fields surrounding the parts,and which would give rise to radio interference if allowed to rise highenough to give sparkover.

The same effect of equalizing potential differences between the body andarm may be achieved by using semiconducting materials such as neopreneor natural rubber for the washers 22 as disclosed and claimed inCanadian Pat. No. 576,710 or by providing a metallic bridge.

The casting 16 is provided with a threaded bore in which a bolt 30engages, this bolt 30 holding a keeper plate 31 which has its outer endbent to form a cylindrical groove complementary to that of castingportion 17. The bolt 30 has a compressible insert in the threads toprevent loosening under vibration. A washer plate 32 is interposedbetween the keeper plate 31 and the head of the bolt 30. The innerstraight ends of the plates 31 and 32 fit into a recess 33 formedbetween the casting 16 and a lateral extension of the sideplate 20.

When the clamp formed by casting portion 17 and plate 31 is attached toa cable 1, 2 by tightening the bolt 30 to a required torque, the keeperplate 31 and washer plate 32 both deflect slightly, and thus canmaintain a strong clamping pressure on the cable, preventing this frommoving in the clamp, even if the cable compresses slightly after thebolt has been finally tightened. Further particulars of this clampingarrangement, with details of the plates 31 and 32 required forparticular cables, are given in our copending patent application Ser.No. 829,263 filed June 2, 1969.

In operation, cable dampers of the type described are clamped to the twocables 1 and 2 which are in the same horizontal plane, the dampers beingspaced at suitable intervals along the cable spans and the clamps beingtightened sufficiently to prevent twisting of the cables within theclamps.

In the event of any transverse vibrations being set up within the cablesby wind forces, the main body will tend to remain substantiallystationary due to its inertia, and the vibrations in the cable, whetherhorizontal or vertical, will tend to produce small angular movements ofthe arms about the pivots formed by bolts 24. The bolts 24 allow formovement of the arms only about the predetermined axes of said bolts,these axes being parallel to the common plane of the cables. Theseangular movements apply shear to the washers 22, which act asenergy-absorbing means since these shear movements of the rubber occurwith a hysteresis loss. The washers 22 bias the arms into the neutralposition as shown in the drawing so that the cables tend to oscillateabout this position. Since the axes of the arms 15 are inclined atapproximately 45 to the common plane of the cables, the small angularmovements of the arms about their pivots will be accompanied bytransverse movements in the associated cables in planes which are atapproximately 45 to the common plane of the cables, so that suchmovements have substantially equal components both parallel to the saidcommon plane and perpendicular thereto. Accordingly, when the spacerdamper is mounted horizontally as shown, it is effective to damp outcable vibrations both in the horizontal and vertical planes. It will beparticularly noted that the pivotal movements of arms 15 allows thespacing between the cables to vary, so that damping is particularlyeffective with horizontal vibrations in the two cables which are out ofphase in such a manner as to continuously vary the cable spacing.However, the inertial mass of the body with respect to the conductors issufficient to be effective even when the horizontal motion of theconductors is in phase.

The cable damper shown in FIG. 4 is similar in all respects to that ofFIGS. l-3, except in that the main body 100 is curved as a circular arc.The curvature is such that with the arms 15 extending in the samedirection as the ends of the main body, these arms lie at an inclinationof about 45 to the common plane of the two pivotal axes. All parts ofthis damper apart from the body 100 are the same as those in thefirstdescribed damper, and the same parts are identically referenced.

FIG. 5 shows diagrammatically a spacer damper for holding four cables 1,2, 3 and 4. This damper has a main body in the form of a frame havinghorizontal body members 40 connected at their ends by verticallydisposed connecting members 41. The members 40 and 41 together form arigid rectangular frame, and pivotal cable clamp arms 15b each holdingone of the four cables extend from the corners of the frame each at anangle of about 45 to the sides of the frame. The arms 15b areattached'to the corner points of the frames by resilient energyabsorbing means, allowing a limited degree of pivoting around a neutralposition, and these arms and their attachment means are identical tothose described with reference to FIGS. l-4. Again, angular movement ofthe arms about the neutral positions (shown) caused by incipientvibrations in the cables allows damped transverse movement of the cablesboth in the common horizontal planes of adjacent cables l and 2, andcables 3 and 4, and also perpendicular thereto.

A frame arrangement may also be used for connecting together more thantwo pairs of cables, for example six or more cables, still allowing eachcable damped transverse movement of the cables with components both inthe common horizontal planes of adjacent cables, and in planesperpendicular thereto. Such frames would include three or morehorizontal body members having pivotal clamp arms extending therefrom atangles of about 45, the arms being connected to the frame by resilientenergy-absorbing means of the type described.

Where two or more pairs of cables at the same potential are suitablyspaced, the use ofa frame arrangement as described is preferable to theuse of several separate two cable connectors, since the frame givesadditional restraint to movements between vertically disposed pairs ofcables, and is particularly effective for damping out vertical, out ofphase vibrations in such pairs.

FIGS. 6 and 6a show a further alternative embodiment of spacer damperfor holding two cables. The main components of the damper are similar tothose of the damper shown in FIGS. l-3 and are similarly referenced butwith the suffix b. In this embodiment, however, the arms 15b extend onopposite sides of a plane passing through the pivotal planes of the twomembers 10b which joins the two pivotal axes and is inclined to thehorizontal common plane of the two cables lb and 2b. Also, the arms 15b,which are approximately half the length of the body member 10b extendapproximately perpendicularly to the body member l0b, when in theirneutral positions. It will be seen from the geometry of this embodimentthat, as in proceeding embodiments, the arms 15b are inclined at about45 to the common plane of the cables lb and 2b.

We claim:

1. A cable damper for damping vibrations in two parallel electricalcables, comprising:

a. a main body, and two arms mounted thereon,

b. said arms carrying cable clamping means for holding the two cablestherebetween,

c. the arms being mounted on the body by pivotal mountings which allowfor pivotal movement of the arms only about predetermined axes parallelto the cables held by said arms,

d. the pivotal mountings for the arms including resilientenergy-absorbing means biasing the arms into neutral positions in whichpositions the arms are inclined to a common plane,

e. said energy-absorbing means being disposed intermediate predeterminedspaces formed by at least a part of each of normally vertically disposedsurfaces of said arms and said body in the area of pivotal connectionthereof so as to prevent contact of said surfaces in operation,

. said energy absorption means being of a thickness sufficient toprovide a compression factor to substantially preclude slippage asbetween the surface of said energy absorption means and the surfaces ofsaid body when pivotal movement occurs,

g. said energy-absorbing means being in the form of normally verticallydisposed and generally disk-shaped resilient washers which are disposedin a plane defining a path transverse of said common plane whereby themaximum shear stress on said washers occurs in a plane per pendicular tothe plane of pivotal movement of said arms,

h. the pivotal movement of said arms on said body being such that therange of angular movement of an arm about said neutral position such ascan be caused by vibrations of a cable attached thereto lies betweenplanes through the pivotal axis of said arms respectively parallel toand perpendicular to said common plane,

. wherein said neutral positions of the arms are such that the axis ofeach arm passing through the center of the clamped cable and the pivotalaxis of the arm lie at an inclination of between 25 and 65 to the saidcommon plane.

2. The cable damper defined in claim I wherein each washer has one facein contact with the surface of an arm of said damper and the other incontact with the body of said damper.

3. The cable damper defined in claim 1 wherein the faces of each washerare provided with deformations for gripping with mating surfaces on thearm and body of said damper.

4. The cable damper defined in claim 3 wherein said deformations of thewashers are radial corrugations and the surfaces of the arms and bodywhich contact the washers have mating corrugations to receive thecorrugations of the washers in gripping relationship.

5. The cable damper defined in claim 1 wherein the energy absorbingmeans are compressed between 18 percent and 25 percent.

6. A cable damper defined in claim 1 wherein the said neutral positionsof the arms are such that an axis passing through the center of a cableclamping means of one arm and the center of the pivotal mounting of thesame arm forms an angle of 45 with an axis which passes through thecenter of the cable clamping means for the two cables.

7. A cable damper according to claim 1, said washers being comprised ofconducting or semiconducting means such as to make an electricalconnection between said arms and said body, said arms and body alsobeing electrically conductive.

8. A cable damper according to claim 1, wherein the body is in the formof a frame having, in addition to the said two arms for holding cablesin a common plane, further arms pivotally mounted thereon, each armhaving clamping means for one cable, and wherein the further anns allowmovement of each cable attached thereto, relative to the frame bothparallel to the said common plane and in a plane perpendicular thereto.

9. A cable damper as defined in claim 1 wherein the said two arms extendon opposite sides of a central plane passing through the axis of thepivotal mounting of the two arms, whereby said central plane is inclinedto a plane which is common to two cables held by said cable-clampingmeans.

10. The cable damper as defined in claim 1 wherein the said resilientenergy absorbing means is comprised of siliconerubber. Y

11. A cable damper as defined in claim 1, wherein stop means areprovided to limit the degree of transverse movement of each cableclamping means relative to the main body.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,609,209

Dated September 28, 1971 Inventor(s) Herbert James HOUSTON et a1 It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Col. 4, Line 48 after "in" delete "Canadian Pat. No. 576,710 add-Canadian Pat. No. 570, 780-- Signed and sealed this 24th day of April1973.

(SEAL) Attest:

EDWARD I 1.PLETCHER,JR.

Commissioner of Patents O-IQSO I 10-59) USCOMM-DC 60375-P69 9 U 5GOVERNMENT PRINYING OFFICE I969 O366334 I

1. A cable damper for damping vibrations in two parallel electricalcables, comprising: a. a main body, and two arms mounted thereon, b.said arms carrying cable clamping means for holding the two cablestherebetween, c. the arms being mounted on the body by pivotal mountingswhich allow for pivotal movement of the arms only about predeterminedaxes parallel to the cables held by said arms, d. the pivotal mountingsfor the arms including resilient energy-absorbing means biasing the armsinto neutral positions in which positions the arms are inclined to acommon plane, e. said energy-absorbing means being disposed intermediatepredetermined spaces formed by at least a part of each of normallyvertically disposed surfaces of said arms and said body in the area ofpivotal connection thereof so as to prevent contact of said surfaces inoperation, f. said energy absorption means being of a thicknesssufficient to provide a compression factor to substantially precludeslippage as between the surface of said energy absorption means and thesurfaces of said body when pivotal movement occurs, g. saidenergy-absorbing means being in the form of normally vertically disposedand generally disk-shaped resilient washers which are disposed in aplane defining a path transverse of said common plane whereby themaximum shear stress on said washers occurs in a plane perpendicular tothe plane of pivotal movement of said arms, h. the pivotal movement ofsaid arms on said body being such that the range of angular movement ofan arm about said neutral position such as can be caused by vibrationsof a cable attached thereto lies between planes through the pivotal axisof said arms respectively parallel to and perpendicular to said commonplane, i. wherein said neutral positions of the arms are such that theaxis of each arm passing through the center of the clamped cable and thepivotal axis of the arm lie at an inclination of between 25* and 65* tothe said common plane.
 2. The cable damper defined in claim 1 whereineach washer has one face in contact with the surface of an arm of saiddamper and the other in contact with the body of said damper.
 3. Thecable damper defined in claim 1 wherein the faces of each washer areprovided with deformations for gripping with mating surfaces on the armand body of said damper.
 4. The cable damper defined in claim 3 whereinsaid deformations of the washers are radial corrugations and thesurfaces of the arms and body which contact the washers have matingcorrugations to receive the corrugations of the washers in grippingrelationship.
 5. The cable damper defined in claim 1 wherein the energyabsorbing means are compressed between 18 percent and 25 percent.
 6. Acable damper defined in claim 1 wherein the said neutral positions ofthe arms are such that an axis passing through the center of a cableclamping means of one arm and the center of the pivotal mounting of thesame arm forms an angle of 45* with an axis which passes through thecenter of the cable clamping means for the two cables.
 7. A cable damperaccording to claim 1, said washers being comprised of conducting orsemiconducting means such as to make an electrical connection betweensaid arms and said body, said arms and body also being electricallyconductive.
 8. A cable damper according to claim 1, wherein the body isin the form of a frame having, in addition to the said two arms forholding cables in a common plane, further arms pivotally mountedthereon, each arm having clamping means for one cable, and wherein thefurther arms allow movement of each cable attached thereto, relative tothe frame both parallel to the said common plane and in a planeperpendicular thereto.
 9. A cable damper as defined in claim 1 whereinthe said two arms extend on opposite sides of a central plane passingthrough the axis of the pivotal mounting of the two arms, whereby saidcentral plane is inclined to a plane which is common to two cables heldby said cable-clamping means.
 10. The cAble damper as defined in claim 1wherein the said resilient energy absorbing means is comprised ofsilicone-rubber.
 11. A cable damper as defined in claim 1, wherein stopmeans are provided to limit the degree of transverse movement of eachcable clamping means relative to the main body.